Community challenge #10: Milling plastics (closed)

Entry #3 (Butterfly Lamp)

My 5yo daughter didn’t want to be left out of the “new room” stuff, so she requested a rainbow lamp. As soon as I got the LED “neon” lights in from China, I started working on a design. She then changed her mind and wanted a butterfly lamp. Because she’s pretty much in charge around here, I told her that would be no problem.

I went full plastic on this one. The lamp is made of white expanded PVC (0.75” & 0.5”), translucent light diffusing 3mm cast acrylic, and cellophane sheets.

First, the final result:

Started with some options for the design (to run by the bosses) in Inkscape.

Made sure the bottom was flattened and everything was symmetrical. Ended up deciding against the antennae because they would ultimately be broken (by kids, not during machining). Boss didn’t approve of that decision, so I gave her a compromise that I knew she’d like.

Pulled the SVG into Fusion for the final CAD, but mostly just the CAM. Inkscape was the design workhorse on this one.

Front was made from a sheet of ½” PVC. I pocketed the inside to a depth of 8mm using an adaptive toolpath.

¼” Single Flute

Feed: 2500mm/min (could definitely do 3500)

Speed: Dewalt on two-ish

DOC: Full 8mm

Followed that with contours to clean the inner perimeter, cut the holes, and cut the part out.

The middle piece is ¾” PVC just to add thickness, so it is just an “outline”.

I was a little nervous about this middle part becoming really flexible, and I tried out the “Thin Wall” feature in Fusion 360. Basically, it alternates machining inside and outside profiles to keep the forces balanced….kinda cool. It’s really meant for machining super thin metal features, but definitely something that I hope to remember.

The back is also ¾” PVC. This is similar to the front without the holes.

Cut full depth (15mm) with an adaptive toolpath at 3000mm/min…Love watching it cut PVC!

Used an external, inline switch on this one, so I just soldered the bright white led strip straight to a barrel connector and ran them around the perimeter.

After that, I cut the acrylic using the same method I used in the other entries. I cut the halves separately because of a changed plan on trying to add the cellophane. Cast acrylic cuts really well.

⅛” single flute upcut endmill (cheap one)

Feedrate: 3210 mm/min

Plunge: 888 mm/min

DOC: 1mm

The HARD part:

To make the openings different colors, I used super thin cellophane sheets. This part made me sweat. It’s like doing a complex glue-up with fast adhesive and tissue paper.

I used 3M spray adhesive (Super 77), and it was basically a mess, but I got better as I went on and it looks good from the outside!

You can see the holes in the previous pic. I used m4 screws to hold the 3 parts together and keep them aligned. I really don’t like gluing PVC together when profiles have to match…it’s too slippery. In hindsight, I should’ve machined some alignment holes. Clamping and drilling afterward worked well.

Some more pics of the final:

Oh…the antenna. I bought a pack of party favor headbands and let my little girl choose the ones she wanted. These were simply screwed into the appropriate spot.

She loves it!

Fusion File: Fusion


A few years ago there was a popular 3D print called a “baker’s cube” or similar.

I never made it since 3D printing wouldn’t be sanitary for food, but thought the concept really cool.

Now I’ve entered the world of CNC, I thought I’d give making one from a solid piece of UHMW a shot.

Due to material costs and size constraints, I’ve chosen the Tablespoon/Teaspoon cube for the challenge.

Started with a 2.5"x2.5"x2.5" cube of UHMW (slippery stuff). Milled it down to 1.6"x1.6"x1.6" final size so I could hold in the Nomad.

Used the Fenrus STLtoPNG to create greyscale to use in Carbide create pro.

Some careful workholding processes allowed the cube to be flipped without losing the WCS.

First trial shown below. I’m staying up way to late again to finish the show piece. I’ll follow up with Cut rocket files as well.


6in Vice Magnetic Soft(er) Jaws

Leftover Delrin and a bench vice that would be more useful if it didn’t mark up objects when clamping.

Soft Jaws Isometric View back 2020-07-04 013112

This one checked off a few boxes for me…

  • Multi-sided machining
  • Chamfering using a vee bit
  • Using a jig with the SO3
  • Having to machine mating parts
  • Machining plastic
  • Broke my personal record for bits used in a job

I built a corner square from scrap plywood (polymer coated on the outsides) so I could make a through cut without damage to my wasteboard, and also because I couldn’t spare any excessive cutting since my work pieces were close to actual size to start off, I needed to be aligned with the axes.

The first side machined was the working face.

  • Facing operation - Freud #75-025 1/4" single flute 18000RPM 60IPM
  • Chamfers and V-grooves - Carbide Tool Source G23 1/4" 90Deg Vee 16000RPM 96IPM
  • Circular groove - Freud #72-101 1/4" 2-flute ball nose 16000RPM 39.371IPM

2nd side was the top side for aesthetics

Last set up was clearing the bulk and magnet holes

Unfortunately, I’m cutting it close. I hit many road bumps a long the way so I have to cut yet another pair, but to give an idea…

Fusion 360 Files



Time is up, voting is open!

Thanks everyone, fantastic entries (again!)

EDIT: oh, and happy 4th of July to all American Shapeokoers ! :us: